Homemade titanium rigging pins

[neuronz]

So I am playing around with the idea of replacing the stainless steel rigging pins on our rig with titanium. Although the stuff is relatively expensive, considering the amount I would need, cost would not really be a factor in absolute terms.

The plan would be to buy some rod and then do the rest myself. However, before I proceed I want to check a few items.

1. Material choice. My plan would be to select a titanium alloy that has higher yield strength than the stainless steel it replaces and increase the safety factors. Grade 5 Titanium looks suitable and is readily available. However, I am no metals expert so is there anything I need to look out for like fatique behaviour or sensitivity to  shear loading or unusual sensitivity to notches.

2. Machining. My plan is to buy some stock in a slightly larger diameter than needed and machine it down. There is a place nearby where I can probably get access to a lath. However, I have only worked with aluminium and steel so far and learned that titanium is difficult to machine and one needs to keep the temperatures low. I am happy to waste some material with trials, but is there anything I need to look out for besides cooling? What is the recommended tool material?

 

[Zonker]

What are you trying to achieve with this little project? Are you stainless pins too weak? Weight savings will be minimal. You could try to find some old Nitronic rod rigging and just cut to length, drill holes for cotter pins at both ends and have a similar result in increased strength.

1. Welding is very hard. Very sensitive to failure if you cold bend it. Typical available Grade 5 (6Al-4V) is plenty strong enough. Shear loading - no issue that I am aware of. Notch (like making a head on pin?). OK, but of course if you're machining from scratch leave a little radius at the junction.

2. Um good luck.  It's quite tricky to learn. This Old Tony on youtube has a video of him learning to machine Ti. 

Ti Grade 5 - mechanical properties of some random round bar. Notice the yield and ultimate tensile strength are very, very close together. This is an extreme example. It does depend on heat treatment but I'd avoid the alloy heat treatments where yield and "BANG" are so close together. 

 

[SloopJonB]

This belongs in Dumb Idea Anarchy.

 

[F_L]

It sounds like a lot of work for little benefit. I am not a machinist but do have a lathe and have learned a few things the hard way. I did a project with titanium grade 5. Tools were indexable carbide inserts and worked fine. It was slow cutting and I  did wear our quite few tips. I did push a dull parting tool a bit too far and ignited the titanium swarf on the lathe bed. It was  a big flash and WTF moment.

 

[bgytr]

Titanium is not so great at the bearing interface.  It wears away.  I was on a boat that had a mainsheet boom fitting made of titanium and we replaced it with steel because the hole was moving towards the edge of the plate as the pin was wearing through it.

 

[Blitz]

Your wire will fail before a pin does.

 

[neuronz]

What are you trying to achieve with this little project? Are you stainless pins too weak? Weight savings will be minimal. You could try to find some old Nitronic rod rigging and just cut to length, drill holes for cotter pins at both ends and have a similar result in increased strength.

1. Welding is very hard. Very sensitive to failure if you cold bend it. Typical available Grade 5 (6Al-4V) is plenty strong enough. Shear loading - no issue that I am aware of. Notch (like making a head on pin?). OK, but of course if you're machining from scratch leave a little radius at the junction.

2. Um good luck.  It's quite tricky to learn. This Old Tony on youtube has a video of him learning to machine Ti. 

Ti Grade 5 - mechanical properties of some random round bar. Notice the yield and ultimate tensile strength are very, very close together. This is an extreme example. It does depend on heat treatment but I'd avoid the alloy heat treatments where yield and "BANG" are so close together. 

View attachment 480612

Some of the pins have been hot glue gun solutions by the previous owner and I have always wanted to replace them for various reasons. A lot of them have been custom made, but not well executed.

For example some are badly machined with grooves and lack bevels which makes them hard to insert. On some actually threads have been added either inside or outside, but they are too short to properly fasten the screws. The ones that hold the spreaders are too short. The list goes on. I figured if I replace them anyway I could just as well do them in titanium since custom parts will be required anyway.

Third question would actually be if I will create corrosion issues with the stainless steel terminals of the rigging?

 

[neuronz]

What's your insurance company say about this idea?

If my insurance company could See the current stuff they should be happy that it is being taken care off. However, I know this is usually not the way the operate. On the other way it is not like I am changing anything from OEM standard since it is a one off and most parts were custom made anyway.

 

[IanA.]

What are you trying to achieve with this little project? Are you stainless pins too weak? Weight savings will be minimal. You could try to find some old Nitronic rod rigging and just cut to length, drill holes for cotter pins at both ends and have a similar result in increased strength.

1. Welding is very hard. Very sensitive to failure if you cold bend it. Typical available Grade 5 (6Al-4V) is plenty strong enough. Shear loading - no issue that I am aware of. Notch (like making a head on pin?). OK, but of course if you're machining from scratch leave a little radius at the junction.

2. Um good luck.  It's quite tricky to learn. This Old Tony on youtube has a video of him learning to machine Ti. 

Ti Grade 5 - mechanical properties of some random round bar. Notice the yield and ultimate tensile strength are very, very close together. This is an extreme example. It does depend on heat treatment but I'd avoid the alloy heat treatments where yield and "BANG" are so close together. 

View attachment 480612

You maybe know this but want to point out

Using scrap Nitronic(50) rigging to make pins will not give the same properties as typically used Nitronic 60 for these applications. Things like hangers and barrel pins for rigging interface are typically milled from N60 for the higher wearing/ fatigue properties.

Ti is really not the best choice for pins/hangers because its properties are not as good in this application. If you are starting the whole design package from scratch using N60 in these areas, you would probably end up with smaller parts for the same SF which further negates any weight savings. 

Not claiming to be an expert but its maybe a point not everyone realizes. 

In this case, the SF's are probably high enough that it might be okay no matter what you use. 

 

[neuronz]

You maybe know this but want to point out

Using scrap Nitronic(50) rigging to make pins will not give the same properties as typically used Nitronic 60 for these applications. Things like hangers and barrel pins for rigging interface are typically milled from N60 for the higher wearing/ fatigue properties.

Ti is really not the best choice for pins/hangers because its properties are not as good in this application. If you are starting the whole design package from scratch using N60 in these areas, you would probably end up with smaller parts for the same SF which further negates any weight savings. 

Not claiming to be an expert but its maybe a point not everyone realizes. 

In this case, the SF's are probably high enough that it might be okay no matter what you use. 

Thanks for this information. Sounds reasonable.

Given that the pin diameters are fixed in this application I would get the 'full' weight saving, although this is not my primary concern. My initial thought actually was that since I do not know for sure the exact properties of the existing pins, going with titanium would be on the safe side and lighter.

Interestingly, titanium seems to be more readily available in small quantities than any Nitronic stainless steel. A quick search turned up very little.

 

[IanA.]

Not only is it way harder to source and super expensive, its also a total pain to work with. 

It would be good to know what sort of pins specifically you plan to replace. You mention spreader pins and also pins with threading. How many are there? How big is the boat? 

Can we get some photos to pass judgement on? 

 

[slug zitski]

Thanks for this information. Sounds reasonable.

Given that the pin diameters are fixed in this application I would get the 'full' weight saving, although this is not my primary concern. My initial thought actually was that since I do not know for sure the exact properties of the existing pins, going with titanium would be on the safe side and lighter.

Interestingly, titanium seems to be more readily available in small quantities than any Nitronic stainless steel. A quick search turned up very little.

When weight savings are sought , hollow pins are used 

 

[DDW]

Even grade 2 titanium is stronger (in yield) than stainless steel unless the stainless is something exotic, like Nitronic. Titanium in gr2 or gr5 isn't that hard to machine, it has to be run at 1/2 or 2/3 the surface speed of 316 SS. You do have to be careful of the swarf which will catch fire as mentioned, and is spectacular when it does. It generates a good amount of heat when cutting (gr2 more than gr5) so coolant is highly desirable. There are titanium specific inserts, but any good non-ferrous carbide insert will do it. Drilling the small holes needed for split pins will be ... interesting. The great advantage of something like 316 for this is while not particularly strong, it does have a much more graceful failure than many other materials, elongating and getting harder as it telegraphs impending failure. 

 

[neuronz]

Not only is it way harder to source and super expensive, its also a total pain to work with. 

It would be good to know what sort of pins specifically you plan to replace. You mention spreader pins and also pins with threading. How many are there? How big is the boat? 

Can we get some photos to pass judgement on? 

So there are multiple sets of pins and bolts on the rig.

1. Halyard sheave pins. IIRC these are 8mm diameter cut from stock with a cotter pin on each side. They are OK-ish, but also easy to replace. 5 pieces.

2. Rigging pins. 6 rigging pins of varying diameter (approx. 5-8mm depending on the shroud size). These are custom made for each set of shrouds and are badly machined and lack bevels. They are a PITA to insert. I think one would have to significantly reduce the diameter if the grooves were to be removed by re-machining.

3. Spreader bolts. Each spreader is attached with two rather large diameter vertical bolts to the spreader bars. These are too short as they end inside the (non- self securing) nuts that secure them. 8 bolts in total.

4. Spreader tips. The rigging is discontinous so at the first spreader there is one horizontal pin each side where the terminals meet. They are threaded on the inside on one end and 'secured' with a tiny screw. They are badly machined and difficult to get in and out. The thread is fairly short.

5. Headstay attachment pin. This one is completely ridicolous. Someone took a pin and then put a thread on the end and screwed an eyelet to it because he did not have nut or something.

6. Backstay attachment pin. The only proper pin on the rig IMO. It just fits.

So that makes 22 to replace in total. Boat is an 8m performance boat. I will try to find some pictures.

 

[SloopJonB]

What's your insurance company say about this idea?

Has anyone ever had their insurance company ask what their rigging pins are made of - or who made them?

My headstay fitting, chainplates, boom & vang goosenecks and rudder shaft are all Ti - my insurance companies have neither known nor cared about it.

 

[221J]

You won't find titanium with the toughness of stainless.  Look at the notch sensitivity values.  Steel is really good at prevent a small defect from growing.  There is no way to inspect and find a fatal defect in titanium.  This is a condensed version of what I learned working with the USN for a decade.

This is not a good idea.  A titanium bike is a much better idea.

 

[casc27]

This belongs in Dumb Idea Anarchy.

And all this time I thought DIA was this whole f'ing s(h)ite. Returns to wallowing in ignorance...

 

[SloopJonB]

And all this time I thought DIA was this whole f'ing s(h)ite. Returns to wallowing in ignorance...

Relativity is a thing.

There is a huge amount of valuable knowledge and experience available here. More than anywhere I know.

You just have to be able to separate the wheat from the chaff.

Or the valid knowledge from the invalid opinion as the case may be.

Now... as to the perfect anchor...

 

[Captain Jack Sparrow]

So I am playing around with the idea of replacing the stainless steel rigging pins on our rig with titanium. Although the stuff is relatively expensive, considering the amount I would need, cost would not really be a factor in absolute terms.

The plan would be to buy some rod and then do the rest myself. However, before I proceed I want to check a few items.

1. Material choice. My plan would be to select a titanium alloy that has higher yield strength than the stainless steel it replaces and increase the safety factors. Grade 5 Titanium looks suitable and is readily available. However, I am no metals expert so is there anything I need to look out for like fatique behaviour or sensitivity to  shear loading or unusual sensitivity to notches.

2. Machining. My plan is to buy some stock in a slightly larger diameter than needed and machine it down. There is a place nearby where I can probably get access to a lath. However, I have only worked with aluminium and steel so far and learned that titanium is difficult to machine and one needs to keep the temperatures low. I am happy to waste some material with trials, but is there anything I need to look out for besides cooling? What is the recommended tool material?

https://www.fisheriessupply.com/allied-titanium-pins-clevis-grade-5-titanium

You could just order what you need from them, if cost really isn't a factor.  

I'm a bit curious why the stainless pins don't fit. Poor sizing selection by previous owners for various pins doesn't mean that stainless is a bad idea. Are the pins going into worn out fittings? Maybe the pins are fine and every fitting on the boat needs to be replaced? 

Thanks for this information. Sounds reasonable.

Given that the pin diameters are fixed in this application I would get the 'full' weight saving, although this is not my primary concern. My initial thought actually was that since I do not know for sure the exact properties of the existing pins, going with titanium would be on the safe side and lighter.

Interestingly, titanium seems to be more readily available in small quantities than any Nitronic stainless steel. A quick search turned up very little.

So because you don't know what the exact properties are of your existing clevis pins, machining custom rigging pins with a material that is widely known to be difficult to work with is going to be on the safe side?